﻿using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
 
namespace ExtraFoundation.Components
{

    [AddComponentMenu("UI/Effects/Gradient")]
    public class UIGradient : BaseMeshEffect
    {
        #region Public Declarations
        public enum Type
        {
            Vertical,
            Horizontal
        }
        #endregion

        #region Public Properties
        public Type GradientType = Type.Vertical;
        [Range(-1f, 1f)]
        public float Offset = 0f;
        public Gradient gradient;
        #endregion

        #region Public Methods
        public override void ModifyMesh(VertexHelper helper)
        {
        if (!IsActive() || helper.currentVertCount == 0)
        { return; }

        vertexList.Clear();
        helper.GetUIVertexStream(vertexList);

        int nCount = vertexList.Count;
        switch (GradientType)
        {
            case Type.Vertical:
            {
                float fBottomY = vertexList[0].position.y;
                float fTopY = vertexList[0].position.y;
                float fYPos = 0f;

                for (int i = nCount - 1; i >= 1; --i)
                {
                    fYPos = vertexList[i].position.y;
                    if (fYPos > fTopY)
                        fTopY = fYPos;
                    else if (fYPos < fBottomY)
                        fBottomY = fYPos;
                }

                float fUIElementHeight = 1f / (fTopY - fBottomY);
                UIVertex v = new UIVertex();

                for (int i = 0; i < helper.currentVertCount; i++)
                {
                    helper.PopulateUIVertex(ref v, i);
                    v.color = gradient.Evaluate((v.position.y - fBottomY) * fUIElementHeight - Offset);
                    helper.SetUIVertex(v, i);
                }
            }
            break;
            case Type.Horizontal:
            {
                float fLeftX = vertexList[0].position.x;
                float fRightX = vertexList[0].position.x;
                float fXPos = 0f;

                for (int i = nCount - 1; i >= 1; --i)
                {
                    fXPos = vertexList[i].position.x;
                    if (fXPos > fRightX)
                        fRightX = fXPos;
                    else if (fXPos < fLeftX)
                        fLeftX = fXPos;
                }

                float fUIElementWidth = 1f / (fRightX - fLeftX);
                UIVertex v = new UIVertex();

                for (int i = 0; i < helper.currentVertCount; i++)
                {
                    helper.PopulateUIVertex(ref v, i);
                    v.color = gradient.Evaluate((v.position.x - fLeftX) * fUIElementWidth - Offset);
                    helper.SetUIVertex(v, i);
                }
            }
            break;
            default:
            break;
            }
        }
        #endregion

        #region Internal Fields
        private List<UIVertex> vertexList = new List<UIVertex>();
        #endregion
    }
}